1. Field of the Invention
The present invention relates to a color filter comprising a retardation control layer for improvement of reflection prevention properties or viewing angle and suitable for indicating various displays particularly liquid crystalline displays in color, as well as a method for manufacturing the same. The present invention relates to a display constituted of the color filter comprising a retardation control layer.
2. Description of the Related Art
Various types of displays have been practically used, and these displays are applied often by combining a retardation control layer with a linear polarizing plate or the like. For example, a circularly polarizing plate consisting of a combination of a linear polarizing plate and a ¼ wavelength retardation plate or a combination of a ½ wavelength retardation plate, a ¼ wavelength retardation plate and a linear polarizing plate is arranged at the observation side of an electroluminescence display thereby preventing light reflection to improve display contrast. In reflective liquid crystalline displays or semi-permeable and semi-reflective liquid crystalline display, a circularly polarizing plate or ellipse polarizing plate is used to utilize the light shutter effect of liquid crystalline molecules. For improving color compensation and viewing angle characteristics of supertwisted nematic mode liquid crystalline displays, retardation plates have been utilized. Particularly in vertically oriented mode liquid crystalline displays capable of high contrast display in recent years, a retardation film (negative C plate) having negative birefringence anisotropy with an optical axis perpendicular to a substrate is used in combination with a retardation film (positive A plate) having positive birefringence anisotropy with an optical axis parallel to a substrate (for example, JP-A No. 10-153802 (pages 12 to 13, FIG. 54).
As the retardation control layer in such a display, a stretched polycarbonate film, or a retardation control film obtained by applying a liquid crystalline material having birefringence anisotropy onto a triacetyl cellulose film or the like, is used, but an adhesive layer used in attaching the retardation control layer to a linear polarizing plate to form a laminate or in further attaching the laminate to a laminate display may cause light reflection, and the thickness of the retardation plate is not negligible.
Formation of a retardation layer by laminating a polymerizable liquid crystalline material on a color filter is also conceivable, but the retardation required of the retardation plate is varied depending on the color (which is actually the wavelength of transmitted light) of each pattern constituting the color filter; for example, when the central wavelength of red light is 650 nm, the central wavelength of green light is 550 nm, and the central wavelength of blue light is 450 nm, the retardation required of a ¼ wavelength retardation plate is 650/4=163 (unit: nm) for red light, 550/4=138 for green light, and 450/4=113 for blue light.
Accordingly, a linear retardation plate and a retardation plate having a retardation of 138 nm are usually used in order to realize circularly polarized light in green of highest visibility, but deviation from circularly polarized light occurs in a narrow sense in red and blue so that when a mirror surface is observed via a circularly polarizing plate made of this retardation plate under a white light source, reddish purple color is observed due to leakage of red and blue lights, which is problematic upon use in prevention of reflection. For use in improving the viewing angle characteristics of liquid crystalline displays, optical designing is conducted mainly in green so that upon indication in black subjected to compensation of viewing angle is diagonally observed, the observed black assumes reddish purple due to leakage of red and blue lights.